Manufacture of ferromagnetic material



Aug. 7, 1945, D. A. OLIVER MANUFACTURE OF FERRO-MAGNETIC MATERIAL FiledSept. 22, 1941 FIG. 4.

FIG. 3.

Patented Aug. 7, 1945 UNITED STATES PATENT OFFICE MANUFACTURE OFFERROMAGNETI C MATERIAL Donald Arthur Oliver, Sheflield, England,assignor to William Jessop & Sons Limited, Sheifield,

England Application September 22, 1941, Serial No. 411,936

In Great Britain September 21, 1940 (Cline-1o) 4 Claims. Granted Thisinvention relates to the manufacture of ferro-magnetic material by aprocess of the kind in which anisotropic magnetic'characteristics aredeveloped by subjecting the material to a magnetic field during coolingfrom an elevated temperature which is'usually one above the Curie point,the object of the invention being to provide an improved process of thiskind for enabling latent magnetic properties of ferro-magnetic ma terialto be developed in a controlled manner.

More particularly the object is to enable optimum magnetic properties insuch material to be developed for purposes such as the employment of thematerial in magneto-generators or in transformers. l

Other objects are implicit in the following description of theinvention.

Hitherto the anisotropy produced by subjecting form-magnetic material toa magnetic field under the provisions of sec; 14, actof March 2, 1927;357 O. G. 5

The relatively rotating ferro-magnetic material and field maybe co-axialor units of material may be grouped around the axis of rotation,

Apparatus for maintaining the relative rotation of term-magneticmaterial and magnetic field may comprise a bi-polar magnetic system,

which may be energised by a permanent magnet or magnets or by continuousor alternating electric current, a carrier mounted in bearings to 1'0-tate in a gap between polanfaces of the magnetic system about an axis atright angles to the direction of the field, means for attaching theheated material to the carrier and means for rotating above, to onebelow, the Curie point to a magnetic field which is concentrated alonglines extending in both dimensions of such planar zones.

Thus, for example, the characteristics may be enhanced, for example,along all diametrical lines of material in cylindrical or disc-likeform.

The invention is particularly applicableto high coercivity material,such as for example, an iron base alloy containing 13% to 30% of cobalt,8%

'a spigot and socket joint.

, netic material.

' the latter.

The carrier may vary in construction according to the form or shape ofthe material to be treated. Thus for material having axial grooves oreccentric apertures the carrier may comprise heat resistant rods groupedaround the axis of rotation and each in two portions connected by may beattached to the carrier by separting' the rods thereof at their'joints,causing them to engage the grooves or apertures in the material "andre-connecting them.

When the material has a central aperture the carrier may comprise amandrel and heat resistant supports projecting radially therefrom andadapted to engage the aperture in the ferro-mag- In a modification aflange may project from the mandrel at right angles to the axis ofrotation and means be provided for clamping the ferro-magnetic materialagainstthe flange.

In all cases the anisotropic character of high coercivity materialmanufactured accordingto the present invention is not impaired bysubsequent demagnetisation or magnetisation in any to 20% r nickel and5% to 10%. of aluminium,

although it may also be applied to high permeability material. w

In the method of producing the desired aniso- I to the planar zones inwhich the multi-directional characteristics of augmented value are to beproduced. Thus the materialmay be rotated in the magnetic held or may bestationary in a rotating magnetic field set up by a three-phase statorsystem of alternating electric currents.

direction and, before use, such material may be, and preferably, isre-magne'tised in the desired directions'in the planar zones in whichits magnetic characteristics have been enhanced.

In the accompanying drawing:

Figure 1 is a longitudinal section of 9, device according to the presentinvention for rotating ferro-magnetic material in a magnetic field.

Figure 2 is a transverse section on the line 2-2 asu I A Figures 3 and 4are diagrams illustrating apparatus for carrying out the presentinvention.

Like reference numerals indicate like par throughout the drawing.

With reference first to Figures 1 and 2 the deviceillustrated comprisestwopole-pieces l0 and l I of soft iron which are adapted to form part ofThe heated material a bi-polar magnetic system as hereinafter describedwith reference to Figures 3 and 4.

The gap between the pole pieces II and H is enclosed by plates ofnon-magnetic material, one end plat I! and the two side plates it and Ibeing more or less permanently secured by screws II tothe pole pieces IIand thus forming a box-like contrivance. The other end plate is isdetachably attached in place by dowel pins H.

In the particular example illustrated thematerialtobetreatedisintheformofadisc ll having axial slots is in itsperiphery and a carrier for the disc is is rotatably mounted in ballbearings. 20 and 2i respectively secured in the end plates l2 and it.This carrier is of a cagelike construction comprising end discs orspiders 22 and 23 connected by heat resistant rods 24. Each of the rods24 is in two portions connected by spigot and socket Joints indicated at20. The end disc 22 of the carrier has a tapered trimnion 2| detachablyengaged with the inner race the ball bearing and the end disc 23 hasrection the disc a remanence of 2,000 gauss, a coercive force of 220oersteds and a (BI'Dmax of 820,000.

A sample'of the same alloy possessing isotropic magnetic characteristics(1. e. heat treated without the influence of a magnetic field to giveoptimum properties) has aremanence of 0,000

gauss, a coercive force of 50 oersteds and a (Bl-Um of 180,000. Thus thetreatment of a cylindrical body in the apparatus described aboveaccording tothe present invention result inv augmenting the magneticvalues along all diameters of any section perpendicular to the axis incomparison not only with the values in the direction of the axis of thatbody but also with the values in an direction of an isotropic of thesame material. 'What I claim is:

l. The method of producing anisotropic properties-in ferroemagneticmaterial such that magnetic characteristics are enhanced in diilerent aspindle portion 21 mounted in the inner race i I of the ball bearing IIand carrying on the other side of the end plate It a pulley as by meansof which the carrier-may be rotated.

It will be appreciated that the pole pieces I0 and I I are comprised ina bi-polar magnetic system which, as indicated in Figure 3, may beener-.

gized by a continuous or alternating electric current passing round thecoils in. If desired, however, the magnetic system may be energized by adirections in parallel planar zones, in comparison with the likecharacteristics in directions having a component at right angles to suchplanar zones, by subjectingthe material during cooling from atemperature above to one below the Curie point to a magnetic field andby mainpermanent magnet I0 as indicated in Figure 4..

In use the end plate It is detached from the pole pieces II and Hcarrying with it the complete carrier. The carrier is then separated atthe spigot and socket joints 2! of the heat resistant rods 20 and thespigots of the latter are then engaged in the grooves ll of the disc IIwhich is at a temperature above the Curie point and preierably in theneighbourhood of 1200' C. The carrier is then replaced in the gapbetween the pole pieces II and II, this. operation being facilitated bythe tapered formation of the end of the trunnion 2!. Whilst thetemperature of the material '10 is still above the Curie point the cageis drivenby power applied to the pulley II thereby rotating the materialII in the magnetic ileld between the pole pieces II and II.

' In a particular example a disc of high coercive material consisting ofan iron base alloy con- 1 talning 24.9%- of cobalt, 11.1% of nickel,6.8%

p of aluminum, 2.3% of copper, 0.08% of carbon.

and 2.1% of titanium, was cast in disc form which was raised to atemperature of 1200 0., placed in the device illustrated in Figures land2 and rotated at a speed of 000 revolutions per minute in a magneticfield strength of 5,000 oersted until cooled to a temperature of about600 C. The disc was then removed from the apparatus and was found topossess in all directions in the plane of the disc a remanenee of 10,000gauss, a coercive force-of 400 oersteds and a (BH)max of 2,000,000.Measured in an axial ditaining relative rotation between the materialand the magnetic field, during cooling of the Inaterial past the Curiepoint, about an axis at right angles to the planar zones in which themulti- Idirectional characteristics of augmented value are to beproduced. a

2. Themethodasinclaimlinwhichthematerial is rotated in the magneticheld.

3. The method of producing anisotropic properties in ferro-magneticmaterial such that magnetic characteristics are enhanced in diiferenidirections in parallel planar zones, in comparison with the likecharacteristics in direetiml having a component at right angles to sue!planar zones, by subjecting the material durim cooling from atemperature above to one balm the Curie point to a rotating magneticheld as up by a three-phase stator system of alternatinl electriccurrents causing the said ileld to rotat about an axis at right anglesto the' planar none in which the multl-directional characteristics 0augmented value are to be produced.

4. The method of producing anisotropic prop erties in high coercivitymaterial consisting of a: iron base alloy containing 13% to 30% ofcobalt 8% to 20% of nickel and 5% to 10% of aluminum by subjecting abody of such alloy during cool ing from a temperature above to one belowth Curie point to a magnetic held and by maintain ing relative rotationbetween the said body an the magnetic field, during cooling of the bodpast the Curie point, about an axis at right angle to the planar zonesin which the multi-direc tional characteristics of augmented value are ibe produced.

DONALD ARTHUR OLIVER.

